Grinding wheel dresser



May 5, 1942; l. J. SNADER I GRINDING WHEEL DRESSER Original Filed July 26, 1958 8 Sheets-Sheet l INVENTOR pa]: snadt pauog TTORNE Y y 1942- I.I. J. SNADER 2,281,723

GRINDING WHEEL DRESSER Original Filed July 26, 1938 8 Sheets-Sheet 2 IN VENTOR By v rrafsnader A TTORN Y6.

May 5, 1942. l. J. SNADER GRINDING WHEEL DRES SER Original Filed July 26, 1938 8 Sheets-Sheet 3 an n..- 4'

11 in. L3: In, I IIHHII ilm L IIVVVENTOR By Irafnader I a Wm M 7,47T0RNE Ys.

y 5, 1942- l. J. SNADER 2,281,723

GRINDING WHEEL DRESSER Original Filed July 26, 1938 8 Sheets-Sheet 4 IN'VENTOI? M A TTORNE m May 5, 1942.

Original Filed July 26, 1938 l. J. SNAD GRINDING WHEEL DRESSER 8 Sheets-Sheet 5 M 4 fi a TTORNE ys.

May 5, 1942. l. J. SNADER GRINDING WHEEL DRESSER Original Filed July 26, 1938 7 8 Sheets-Sheet 6 INVENTOR v Ira. sna-def- M MMTTORNEKS.

y 1942. l. J. SNADER 2,281,723

GRINDING WHEEL DRESSER Original FiledJuly 26, 1958 8 Sheets-Sheet 7 $.49;- 126.0 5 INVENTOR 2 a v, D Z; 7 L Ira. Snaoler A TTO 5 K9. 2:2 m: M M

l atented May 5, 1942 GRINDING WHEEL DRESSER Ira J. Snader, Detroit, Mich., assignor to Ex- Cell-O Corporation, Detroit, Mich., a. corporation of Michigan Original application July 26, 1938, Serial No.

221,374. Divided and this application December 16, 1940, Serial No. 370,382

21 Claims.

The invention relates generally to grinding machines embodying a grinding wheel and it has particular relation to a dresser for dressing the surfaces of the wheel.

As a generality, it will be understood that grinding machines employing form grinding wheels are utilized to generate forms on different types of work. In particular, the present invention is concerned principally with thread grinding machines having grinding wheels designed to generate a thread on the work, and an important reason for using such machines is to obtain precision in the formation of the threads. During the use of such grinding wheels, wear on the grinding surfaces naturally occurs and it is customary to dress such surfaces by means of diamond dressing tools, so as to promote uniformity in precision obtained. Inasmuch as the dressing operation is not a work producing operation, it is important that the former be performed rapidly and with minimum interference with the work grinding operation so that the work producing capacity of the grinding machine will be as great as possible.

This application constitutes a division of the application for patent of Harold N. Seyferth and Ira J. Snader, Serial No. 221,374, filed July 26, 1938.

One of the principal objects of the invention is to provide a machine for dressing form generating surfaces of a grinding wheel which will enable dressing such surfaces in a minimum amount of time and with a high degree of precision.

Another object of the invention is to provide a dressing machine of the above identified character, having adjustment means of such character that the dressing tools may quickly and accurately be positioned.

Another object of the invention is to provide an improved machine for dressing a thread generating form on a grinding wheel which employs a pair of diamond dressing tools that are designed and arranged to dress respective grinding sur faces of the wheel.

Another object of the invention is to provide a dressing machine of the general type indicated wherein each of the diamond dressing tools, at the end of its particular dressing operation, is separated from the dressed surface and then is returned to its original position while being maintained in spaced relation to the dressed surface.

Another object of the invention is to provide a dressing machine such as mentioned, which is controlled and operated hydraulically.

Another object of the invention is to provide a form dressing machine which is so designed, constructed, and arranged that by means of a readily variable relation of parts, the machine may be used for dressing grinding wheels varying widely in form or contour.

Other objects of the invention will become apparent from the following specification, from the drawings relating thereto, and from the claims hereinafter set forth.

For a better understanding of the invention, reference may be had to the accompanying drawings, wherein:

Figure 1 is a view in perspective of a thread dressing machine constructed according to one form of the invention;

Fig. 2 is a front elevational view of the machine shown by Fig. 1;

Fig. 3 is a rear elevational view of the machine shown by Fig. 1;

Fig. 4 is a side elevational view of the machine shown by Fig. l, with certain parts shown in section;

Fig. 5 is a cross-sectional view taken substantially along the line 5-5 of Fig. 2;

Fig. 6 is a cross-sectional view taken substantially along the line li6 of Fig. 5;

Fig. 7 is a cross-sectional view taken substantially along the line l-l of Fig. 6;

Fig. 8 is a cross-sectional view taken substantially along the line 88 of Fig. 2;

Fig. 9 is a cross-sectional view taken substantially along the line 9-9 of Fig. 8;

Fig. 10 is a cross-sectional view taken substantially along the line Ill-ill of Fig. 8;

Fig. 11 is a fragmentary, sectional view of the outer peripheral portion of a thread grinding wheel, showing the manner in which the surfaces of the wheel are dressed during operation of the machine;

Figs. 12, 13, and 14 are sectional views of the valve employed for controlling operation of the machine; and

Fig. 15 is a detail view in section showing the mounting of the diamond holder and the manner of adjusting it.

Referring to Figs. 1, 2, and 3, a fixed base portion of the grinding machine is indicated at It and the entire dresser shown by these figures is so mounted on this base portion that the grinding wheel may be brought into a proper position to be dressed in the manner hereinafter to be stated.

A slide H is on the base H! by means of a dovetail l2 and slot l3 receiving the dovetail and the slide may be adjustably fixed in position by means of a gib 14 at one side of the slot. This gib is adapted to be forced against one side of the dovetail by means of a screw l5 threaded through a portion of the slide and which has its inner end projecting into a non-threaded opening IS in the bar. It is apparent that as the screw is tightened, the bar I4 is pressed frictionally against the side of the dovetail I2 so as to lock the base and slide together. A lock nut ll, on the outer end of the screw, locks the latter in position after the adjustment is made.

As shown by Figs. 1 and 2, the slide ii has a concentric guideway [8 which receives a complementary guide IS on a bracket swivel 20, and as shown by Figures 1 and 5, the base of this swivel has three spaced, arcuate slots 22, 23, and 24 that are concentric to the guideway. The swivel is adjustably secured to the slide H by means of bolts 25 projecting through the slots and threaded into the slide and by loosening the bolts slight ly, the swivel may be swung about the center of the guideway and then by tightening the bolts, the swivel may be fixed in its new position.

In order to secure a fine adjustment of the swivel on the slide, an arcuate bar 21 is secured to the slide, as shown by Figs. 3, 4, and 5, and this bar, as shown by Fig. 4, has teeth 28 on its inner edge which are engageable with teeth 23 on a pin 30 journaled in an adjacent portion of the swivel. At its upper end, the pin 30 has wing portions 3| and 32 through which, respectively, screws 33 and 34 are threaded. As seen by Fig. 4, the inner ends of these pins are adapted to abut a side surface of the swivel and it will be apparent that by loosening one of the screws and tightening the other, the pin 30 will be turned accordingly. This will enable moving the swivel relative to the slide ll owing to the engagement of the teeth 28 and 29. A fine degree of movement of the swivel may be obtained in this manner and the amount of movement may be indicated on bar 21 by employing a marker 35 on the swivel.

It will be understood that the bolts 25 must be loosened before adjusting the positions of the screws 33 and 34 to obtain the fine degree of movement, and ordinarily, the swivel will be so positioned that any movement desired can be accommodated by adjustment of the screws 33 and 34. Should a greater movement be desired, or should it be desired to change the position of the swivel substantially, the pin 30 may be withdrawn and then reinserted after moving the swivel approximately to its new position.

As shown best by Figures 1 and 4, the swivel 20 has an outwardly open and concentric guideway 31 and this guideway receives a similarly shaped dovetail 38 on a U-shape bracket 40. The bracket 40 may be adjustably locked in position relative to the swivel 20 by one or more screws M as shown by Figure 3, which are threaded through a side portion of the swivel and into the guideway 31, so as to frictionally engage at their inner ends one side of the dovetail 38. Thus, by loosening the screws slightly, the bracket may be adjustably swung in a vertical plane, and then looked in its new position by tightening the screws.

Now referring to Figures 2 and 5, in particular, it will be noted that a lead screw extends between the ends of the bracket 40 and has its ends projecting into openings in such ends of the bracket. As shown by Figures 8, 9, and 10, one end of the screw at its under side has a wedge shape slot or groove 49 which receives a similarly shaped projection 50 on a sleeve 5! slidably mounted in an opening 52 in the adjacent end of the bracket. This arrangement prevents rotation of the lead screw about its own axis and it is also apparent that longitudinal movement of the lead screw will depend upon the position of the sleeve 5| along its own axis. If the sleeve is sufiiciently moved in one direction, the projection 50 will completely fill the slot 49 in the screw and thus prevent any movement of the screw longitudinally of its axis while if the projection 50 and sleeve are moved in the other direction, the projection will move towards the larger end of the slot and thus create a space between the projection and the sides of the slot that will permit longitudinal movement of the screw. Rotation of the sleeve about its own axis is prevented by means of a key 54 having a projection 55 that projects into a groove 55 in the under side of the sleeve.

In order to adjust the position of the sleeve 5|, it has a threaded opening 60 at one end and a threaded pin Si is threaded into the opening. The pin at its outer end is journaled in a bushing 62 threaded into the bracket and the outer end of the pin is secured to a knob 63. At its opposite end the sleeve 5| has an opening 64, and a spring 65 seated in this opening and in an apertured cap 66 threaded into the opening in the bracket normally urges the sleeve 5i to the left, as seen in Fig. 8, so as to take up any looseness or play that may be present. When the knob 63 is turned, the sleeve is moved in one direction or the other, depending upon the direction the knob is turned, and movement of the sleeve, as previously stated, causes the wedge 50 to move in the slot 49 in the feed screw 45. The knob 63 has suitable graduated indicia thereon adapted to cooperate with a marker on the bushing 62 so that the permitted movement of the lead screw may be calibrated.

Now referring to Fig. 5, the lead screw 45 has an intermediate threaded portion Ill and a sleeve H is slidably mounted on opposite and smooth portions of the lead screw and has an internally threaded portion 12 at its center which engages the thread on the screw. The opposite ends of the sleeve have close but slidable bearing contact with the smooth portions of the screw and the threads on the screw and sleeve are formed accurately so as to obtain accurate movement when the sleeve is rotated. The sleeve H is rotatable in and carries a body I3 that is movable along the screw with the sleeve, but which is prevented from rotating therewith by means presently to be described. This body has ring portions 14 and 15 disposed around opposite end portions of the sleeve and since the parts arranged between each ring portion and the end of the sleeve are substantially the same, a detailed description of such parts at one end of the sleeve only seems to be sufficient. Referring to the left hand of the arrangement as seen in Fig. 5, the ring portion 14 carries an outer bearing race 16 which is held in position by means of a bearing nut 'l'l threaded into the ring and engaging the race. In order to obtain a completely circumferential contact between the nut and the race 16, a malleable ring 18, constructed of brass, for example, is disposed in a shallow groove in the nut 11 and between the latter and the bearing race. It is evident that the malleable character of the ring 18 will slow it to change in contour under pressure as the nut is threaded into the ring portion 14 and thus obtain a completely circumferential metal to metal contact between the nut and the bearing race. A second nut 80 is threaded into the ring portion and against the nut 11 and between such nuts, a sealing ring 8| may be provided to prevent the escape of lubricant that is provided in the bearing.

The sleeve 1I carries an inner bearing race 83 and between the two bearing races balls 84 are provided. The race 83 is held in position by means of a nut 85 threaded over to the sleeve 1|. It will now be apparent that the sleeve 1| may turn in the body while at the same time being movable therewith axially of the lead screw.

Axially outward of the nut 85, a cam 88 is mounted on the end of the sleeve and this cam is maintained against the end of the nut by means of a friction disc 89 and a nut 90 threaded on the end of the sleeve. The friction disc 89 has a key 9I at one point which is slidablc in a keyway 92 formed in the end of the sleeve, from which it follows that the friction disc is prevented from rotating relative to the sleeve 1|. It may be mentioned that the cam 88 may be adjusted circumferentially upon loosening the nut 90. While the opposite end of the sleeve 1| and the ring portion have similar elements assembled therewith, as described previously with respect to the other end of the sleeve, the cam on the right end of the sleeve has a different function as compared to the cam 98 and for this reason is identified by a different numeral 95.

Between the ring portions 14 and 15, the body 13 has a semi-circular portion I00, which is recessed as indicated at IOI, for receiving a worm wheel I02 disposed on an intermediate portion of the sleeve 1|. While the worm wheel I02 is rotatable relative to the body it is held against axial movement relative thereto by means of finished guide surfaces I03 and I04 slidably fitting opposite faces of the worm wheel. A driving connection is obtained between the worm wheel and the sleeve H by means of keyways I05 and I06 in the sleeve H and wheel, respectively, and a key I01 disposed in both keyways.

Now referring to Fig. 4, the body 13 at the lower side of the lead screw, is provided with spaced walls I08 and I09 that straddle a guide block IIO that is secured by bolts III to an upwardly projecting web II2 on the bracket 40. Between the guide block H0 and the Wall I09, a bar I I3 is provided which is adapted to be held against the guide block in such manner that a desired friction may be provided between the guide block and the bar.

As seen in Fig. 2, three screws H1, H8, and H9 are threaded into the wall I09 and viewing Fig. 4 in conjunction with Fig. 2, the screws II 1 and H9 are relatively short and'hold compression springs I against the bar H3. The intermediate screw I I8 has a pilot |2I at its inner en-i which projects into an opening in the bar II 3 so as to hold the latter relative to body 13 during movement of such body on the guide block while still permitting the bar to be pressed against the guide block by the springs. It will be appreciated that this spring pressure also results in the wall I08 being similarly pressed into frictional contact with the guide block I I0. The purpose of this frictional resistance to movement of the body 13 along the guide block is to prevent movement of the body and associated mechanism along the axis of the lead screw until the latter will first have shifted longitudinally the amount, if any, allowed by the adjustment described in connection with Figs. 8, 9, and 10. As will be understood, the degree of frictional resistance necessary may be obtained by providing a suitable dimension of springs.

Considering the mechanism so far described, it will be apparent that if the worm wheel is 1'0- tated, the parts assembled on the lead screw will move longitudinally thereon after overcoming the friction between the bar II3, wall I08, and the guide block I I0, it being understood that this frictional resistance is such that before any movement of the assembly along the lead screw axis occurs, the lead screw itself will move longitudinally the amount permitted by the adjustment described in connection with Figs. 8, 9, and 10. After the lead screw has moved this limited amount, then continued turning of the worm wheel will cause the assembly on the screw to travel along the latter, during which the frictional force pressing the bar against the block H0 is overcome.

Still referring to Fig. 4, the worm wheel I02 is adapted to be rotated by means of a worm I25 that is keyed to a shaft I26 journaled in a cap I21 which fits between the ring portions 14 and 15 of the body and which is secured to such body by means of screws I30 (shown in crosssection by Fig. 5). Shaft I26 is driven by a hydraulic motor comprising mating gears I3I and I32 on the shaft I26 and on an auxiliary shaft I33, respectively. It may be mentioned that the gears are disposed in openings in a spacer I35 located between the cap I21 and a bearing bracket I31, in which the outer ends of shafts I26 and I33 are journaled.

The hydraulic lines leading to the hydraulic motor and to opposite sides of the motor gears, respectively, are generally indicated at I and MI in Fig. 6. It is to be understood that these lines or openings extend longitudinally in cap I21 and into the motor spacer I35, and while not shown, the openings or lines I40 and MI are connected to vertical openings in cap I21 which join openings I42 and I43, respectively, in the body 13 as seen in Fig. 5. Any leakage of fluid in the motor and along the driven shafts drains through openings leading to various points where leakage may occur and such openings are connected to a drain line I45.

Referring to Figs. 4 and 5 jointly, the three openings I42, I43, and I45 all lead to a valve, generally indicated at I50, and it is to be understood that the drain line I45 is constantly connected to an exhaust port in the valve, The lines I42 and I43 alternately are pressure and exhaust lines so that when hydraulic fluid under pressure is connected to one line, the other line is open to exhaust and it follows that when one of the lines is connected to the fluid under pressure, the hydraulic motor will rotate in one direction and when the other line is connected to the fluid under pressure, the motor will rotate in the opposite direction. While the manner in which the mechanism is to be controlled by operation of the valve will presently be described, it is desired at this time to direct attention to the provision of plungers I58 and I59, as shown by Fig. 3, which have lower inclined faces I56 and I51 adapted to engage a plunger in the valve. These plungers I58 and I59 have their upper ends disposed in the path of movement of bell-crank trips I6I plvotally mounted on the body 13 and which have ends I62, respectively, disposed in the path of movement of pins I65 and I66 on earns 88 and 95. These pins are circumferentially spaced so that one pin moves one trip while the other is substantially displaced from its trip.

Now referring to Figs. 2, 6, and 7, it will be observed that the lower part of the body 13 has a pair of spaced openings I15 and I16 in which diamond carriers I11 and I18 are reciprocably mounted. Each of the carriers as shown by Fig. 7 has a threaded opening I80 and a spring receiving bore I8I, and the openings, respectively, in the two carriers receive adjusting bolts I82 and I83 that are threaded into the openings I80. A spring I85 in each of the bores I8I abuts at one end a shoulder at the inner end of the bore I80 and at its other end a cover plate I86 secured to the body 13, and serves to constantly urge the carrier forwardly. The outer end of each of the bolts I82 and I83 passes through an opening in the plate I86 and is provided with graduated indicia I90 adapted to cooperate with a marker on the plate I86, so that turning movement of the bolts may be measured or calibrated.

At the forward end of each of the carriers as shown by Figs. '1 and 15, an angled opening I9I is provided and these openings, respectively, receive diamond holders I92 and I93 having pointed diamonds I94 and I95, respectively. A set screw I96 is used in conjunction with each of the carriers for holding the diamond carrier against turning about its own axis. Each of the diamond holders has an inclined, rear end face I 91, against which the end of the cooperating adjustment bolt abuts, and from this it will be apparent that when the bolts I82 and I83 are turned, so as to move the bolts forwardly, the diamond holders will be advanced in the angled openings. Since the openings are angled toward each other, as best shown by Fig. 2, this adjustment of the bolts I82 and I83 will advance the diamond points along converging lines.

As shown by Figs. 6 and 7, the carriers I11 and I18, respectively, have offset arms 200 and I at their rear ends, and each of these terminates in a tubular portion 202 extending parallel to the bores I15 and I16. Bushings 203 and 204 are fitted in the tubular portions 202 and are fixed in position by means of set screws 205. Within the bushing 203, a cam follower 206 is reciprocably mounted and the forward end of this follower engages the peripheral face of the cam 88. A bolt 208 provided with graduations 209,

threaded into the rear end of the bushing 203,

serves to adjust the position of the cam follower with respect to the carrier I11.

Similarly, the bushing 204 carried by the arm 20I has a cam follower 2I0 which engages the peripheral face of the cam 95, A second bolt 2I2, shown by Fig. 5, is adjustably threaded into the bushing 204 so that the position of the cam follower 2I0 may be adjusted with respect to the carrier I18.

Again referring to Fig. 6 in particular, it will be observed that the carrier I11 is urged against a block 220 by means of a spring pressed plunger HI and that this block 220 is to the left of the axis of bolt I82 in carrier I11. With respect to carrier I18, it will be noted that the arm 20I thereof is urged against a surface 222 by a spring pressed plunger 223. The reason for these spring pressed arrangements may be stated briefly as follows. It will be apparent that due to the offset relation of the cam followers 206 and 2I0 with respect to the carrier openings I15 and I16 in body 13, engagement of the two cams 88 and 95 with such cam followers will tend to turn the carriers I11 and I18 about the axes of such openings. As will be more evident hereinafter, diamond I94 is engaged with the grinding wheel when cam 88 is turning counterclockwise, as seen in Fig. 7, and hence the frictional engagement of the cam with the cam follower 206 tends to hold the arm 200 positively against the block 220, as seen in Fig. 6. Thus, a solid anchor is provided against altering the position of the diamond during its cutting operation. On the other hand, when the diamond I95 is cutting the grinding wheel, cam 95 is turning clockwise, and the frictional engagement of the cam with the cam follower 2I0 holds the arm 20I solidly against the surface 222.

As shown by Figs. 1 and 4, a cap or cover 225 is provided over the body 13, and this cover is held in position by bolts 226 and 221 threaded into cap I21. These bolts also secure a bar 228 in position that carries a block 229 which is apertured for the purpose of conducting coolant therethrough. A coolant inlet 230 communicates through the block with pipes 23I and 232 which extend to points adjacent the diamonds I94 and I95 so as to supply coolant to the diamonds and grinding wheel during the wheel dressing operation.

It may be pointed out in connection with Fig. 2 that adjustment of the bracket 40 on the bracket swivel 20 occurs about an axial center line indicated at 234, which is centered with respect to both diamonds I94 and I95 and thus adjustment of the bracket causes both diamonds to move about this axial center line. This adjustability, in conjunction with the adjustability of the bracket swivel and the slide II, enables locating the diamonds in the desired positions.

Generally, it will be realized that the path of movement of either of the diamonds is governed jointly by travel of the assembly along the lead screw, the shape of the controlling cam, and by the endwise movement of the lead screw. The latter movement will govern the path of move ment of the diamonds in that the amount of such end movement of the lead screw will govern the time at which axial progression of the diamonds begins, and thus will determine the location of such paths laterally of the grinding wheel. Differently shaped cams may be employed and readily substituted one for another in order to obtain the desired radial movement of the diamonds and the pins on the cams for controlling operation of the motor may be varied in position depending on the results to be obtained. Moreover, the cams may be relatively displaced circumferentially as desired in order to vary the relation of movement of the diamonds. Again, the relation of axial movement may be varied by using a lead screw arrangement with threads of a different pitch or combining this variation with variations in the cams.

In the construction as shown, the cams will not be turned through a complete turn as the pins will reverse or stop the motor before this occurs. Such pins are so related, however, and the cams are so arranged and shaped that as one diamond is moving toward the axis of the grinding wheel, the other is moving away from such axis. The general operation and the character of movement of the diamonds may best be understood in connection with Fig. 11, which shows a grinding wheel 235 and the two diamonds I94 and I95 diagrammatically. It may be mentioned before describing this operation that the shape of the cams necessary to obtain the desired movements of the diamonds may readily be obtained by those skilled in the art. Also, it may be stated that the dressing operation preferably is effected with the grinding wheel operating at the same high rate of speed as that used in the work grinding operation, as then the form is more accurately dressed and moreover, it is not changed such as might be caused by a change in centrifugal force.

As seen in Figure 11, the two points 258 and 25I indicate, respectively, the initial positions of the diamonds I94 and I95, that is, the position of each diamond prior to the beginning of its wheel dressing movement. Assuming that the diamond I95 is at the starting point 250, the diamond I94 will be approximately in the position shown by full lines and indicated at 252. Assuming also that the lead screw is under an adjustment which permits certain endwise movement thereof before the mechanism thereon travels axially of the screw, the diamond I95 will not move until the screw is shifted endwise the amount permitted, as the cam 95 at this time engages its cam follower along a substantially circular portion of the cam. After the lead screw is shifted endwise, the diamond will travel axially of the lead screw until said circular portion of the cam passes its cam follower and then the diamond will travel inwardly towards the center of the grinding wheel along the path 253. The cam is of such character then that the diamond will follow the path 253 so as to dress the upper side of the wheel, as seen in this figure. When the diamond I95 reaches the end of its movement, indicated by the numeral 255, the hydraulic motor reverses and then the lead screw is shifted in the reverse direction the amount permitted. During shifting of the lead screw, rotation of the cam move the diamond in a radial direction substantially to the point indicated at 256. When this point is reached, the mechanism carrying the diamond begins to move axially of the lead screw along the path indicated at 251, and in this connection it will be appreciated that the diamond is separated substantially from the surface of the wheel. While the diamond I95 is moving inwardly to dress the wheel in the manner mentioned, the diamond I94 is returning along its return path of movement, indicated at 258, and it will reach the position indicated at 25I at about the time the diamond I95 reaches the position indicated at 255. cated at 260 shows the path of movement of diamond I94 during its wheel dressing movement and it will be understood that this movement occurs as diamond I95 is returning. Assuming now that the lead screw adjustment is changed so that a greater end movement of the screw is required before movement of the mechanism along the lead screw axis occurs, it will be apparent that the diamond I95, for example, will stay stationary for a longer period of time and therefore a larger circular portion of the cam will pass the cam follower, and from this it will be evident that the diamond will start moving inwardly along a different line such as the line indicated at 262. merit of the diamond will shift laterally of the grinding wheel so as to correspond with the shift from line 253 to 262. Likewise, the path of re- The line indi- It follows that the entire path of moveturn movement 251 will shift laterally but it will be spaced farther from the path of dressing trauma movement due to the greater radial movement at the beginning of the return movement. It follows that if the edge of the grinding wheel is narrower than desired, less endwise movement of the lead screw will be required, whereas if a wider edge on the grinding wheel is present, greater endwise shifting of the lead screw will be necessary. As a generality, therefore, it may be said that adjustability in shifting of the screw endwise enables bringing the two paths of dressing movement of the two diamonds closer together or moving them farther apart, as the case may be, without altering the contour of the paths of movement and while still causing the diamonds to be separated from the dressed surfaces of the wheel during return movement of the diamonds.

It may be mentioned that the wheel shown in Fig. 11 has two inclined surfaces radially inward of the thread form and, in causing the diamonds to travel along these inclined surfaces, the diamonds automatically are resharpened or reshaped to provide new cutting points. This feature is disclosed and claimed in the application for patent of William Locke, Serial No. 212,019, filed June 6, 1938. The present machine is adapted not only to take care of dressing of the wheel form and returning the diamonds in spaced relation to the dressed surfaces, but also to effect this reshaping of the diamonds.

In using the wheel dressing machine, normally the grinding wheel will be dressed at the end of an operation performed by the work grinding machine and it is desirable that operation of the dresser be so controlled as to enable the operator to change the work in the grinding machine while the wheel dressing operation is being effected. The means for controlling operation of the dresser will now be described but before making a detailed description it may be stated generally that the control means is to operate as follows. With the dresser at rest, and with the diamonds located in initial positions 250 and 252, as seen in Fig. 11, the dresser is started by moving a manual control and then it continues its operation automatically until the diamonds return to their initial positions where the dresser is stopped automatically. Thus, the operator need only move the manual control initially.

Now directing attention to Fig. 12, the valve I50 comprises a body 215, a main operating plunger 216 and an auxiliary plunger 211 within the main plunger. The bore in the body which slidably receives the plunger 216 is indicated at 218 and this bore has three exhaust ports 219, 280 and 28I, two pressure ports 282 and 283, two motor line ports 285 and 286 and a pressure port 281 adapted to be temporarily connected to a pressure line. Plates 290 and 29I shown in broken lines for the purposes of clarity and which are bolted to the ends of the body 215 serve as stops for plunger 216 and also provide guides for the operating plungers I58 and I59 described previously.

The plunger 216 has a bore 293 receiving the auxiliary plunger 211 and at its outer surface plunger 216 also has three principal grooves 294, 295 and 296, two pilot line grooves 291 and 298, a drain groove 299 and a starting line groove 30I. Grooves 294 to and including groove 298 are connected by radial openings respectively to the bore 293. Plugs 303 and 304 threaded into the ends of plunger 216 provide end stops for plunger 211 a well as closures for the ends of the plunger.

At the right, a plunger 388 is slidable in the end of plunger 216 and the space at the inner end of plunger 386 is connected by an opening 381 to the bore 293 near the center of the latter. At the left end, a tubular plunger 3I2 having an inner end wall is slidable in the end of plunger 218, and a second plunger 388 is slidable in plunger 3I2. A pin 3I8 passing through the wall of plunger 218 limits outward movement of plunger 3I2 relative to plunger 216. The spac at the inner end of plunger 3I2 is connected to bor 293 by an opening 3 and the space between the inner ends of plungers 388 and 3I2 i in communication with the starting pressure line 281. It may be added here that plates 298 and 29I also serve as stops to limit outward movement of plungers 388 and 388, respectively. Grooves 3I1 and 3I8 are provided in plunger 211 for a purpose which will be understood hereinafter.

Pressure ports 282 and 283 are connected by passages not shown to a hydraulic line indicated at 328 in Fig. 3, exhaust ports 219, 288 and 28I are connected to an exhaust lin 32I, while the starting line port 281 is connected to a line 322. Line 322 as also shown by Fig. 3, extends to a remote control valve 232 which is operable manually. The valve includes a body 321 having a plunger 328 slidable therein and such plunger normally is urged to the right by a spring 329 but is adapted to be moved against the spring by an external, hand control member 338. An exhaust line 33I connected to the body 321 normally is in communication with line 322 through the valve from which it follows that port 281 normally is open to exhaust. A hydraulic line 332 leading to the valve is adapted to be placed in communication with line 322 when the plunger is moved to the left, by a groove 333 in the plunger. it being evident that the plunger when so moved to the left cuts off line 322 from line 33I. It may be noted that both ends of the plunger are open to exhaust at all times by means of an opening 334 extending axially of the plunger and smaller openings 335 at the right end of the former. The size of openings 335 may be such, if desired, to slightly retard spring return of plunger 3I8 so as to hold port 281 in communication with line 332 for a short length of time after hand pressure on the member 338 is released.

Motor line ports 285 and 286, respectively, are connected to the lines I43 and I42 leading to opposite sides of the hydraulic motor, and with the parts in position as shown in Fig. 12, both ports 285 and 286 are connected with the exhaust I groove 295 and, therefore, the motor is stopped and there is no chance of it being moved slightly by any leakage of fluid under pressure to either port. When it is desired to start the cyclic operation, the valve 323 (Fig. 3) is operated and this temporarily admits fluid under pressure to the interior of plunger 3I2 and this causes the latter to shift to the right. At this time, fluid under pressure is present beyond the inner end of plunger 3I2 and thus the fluid therein acts as a hydraulic column, resulting in movement of plunger 216 alon with plunger 3I2. Thi movement connects pressure line 282 and groove 294 to the motor port 285 and connects motor port 286 to exhaust groove 295 and exhaust port 288. The motor thus is caused to rotate in one direction.

When plunger 218 has moved to the right end position, as shown in Fig. 13, pressure port 282 opens slightly to groove 291, and pressure is sup plied to the left end of auxiliary plunger 211 while the right end thereof is open to exhaust port 28I. Auxiliary plunger 211 is thus shifted to the right and when so shifted, the space at the right end of plunger 3I2 is connected by opening 3 and grooves 3I1 and 295 to exhaust port 288.

After the motor rotates sufficiently, plunger I58 is caused to move downwardly by movement of cam 88, and the inclined surface I56 thereon (Fig. 3) engaging a chamfer 325 on the right end of plunger 216, shifts the latter slightly to the left and enough to connect pressure port 283 with groove 296 and hence space 3I8 and opening 381, thereby connecting the space at the inner end of plunger 388 with the fluid pressure line. This results in a shift of plunger 216 to the left to the position shown in Fig. 14, which in turn connects pressure port 283 to groov 296 and motor line 286, and exhaust port 288 to groove 295 and motor line port 285. This causes reversal of the motor.

At the end of the left hand movement of plunger 218, pressure port 283 is opened slightly to groove 298 and fluid pressure is thus supplied to the right end of plunger 211 while the left end of the latter is connected to exhaust. Thus auxiliary plunger 211 is shifted to the left and when so shifted, the space at the inner end of plunger 388 is connected by opening 381 and grooves 3I8 and 295 to exhaust port 288.

When the motor has reversely rotated sufficiently, cam 95 effects downward movement of plunger I59 which in turn engages a chamfer 328 on plunger 216 and shifts the latter slightly to the right sufficiently to open pressure port 282 to groove 294 and opening 3, thus supplying fluid under pressure to the right end of plunger 3I2. This will force plunger 218 to the right until pin 3I8 engages the shoulder on plunger 3I2 and then the parts will stop in position. This brings the parts to the positions shown by Fig. 12.

Starting of the cycle may be re-initiated by operating valve 323, or a manual trigger 338 may be used to shift plunger 218 the initial amount. At both of the end positions of plunger 218, the spaces between its right end and plunger 386, and its left end and plunger 3I2 are open to exhaust and the plunger is held in position by friction only. For this reason the plunger is shiftable by a relatively small force which is normally advantageous for actuating purposes. In some installations, however, where small exhaust lines are used, the exhaust pressure may be considerable and in view of the difference in areas at such ends of the plunger, may be suflicient to shift the plunger at the improper time. For this reason the desired friction is introduced by a split wire ring 331 which creates enough resistance to movement of plunger 216 that the back pressure will not move the plunger.

While the valve is shown in detail, it is to be understood that such valve per se is not a part of the present invention. Electrical controls might be employed to secure the particular cyclic operation mentioned--that is manual start, automatic reversal of the motor, and then stopping of the motor at its initial position. It may be added that a metering valve might be used in the fluid pressure line to vary motor speed.

Although only one form of the invention has been illustrated and described in detail, it will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the appended claims.

What is claimed is:

1. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape for thread grinding purposes, which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support inwardly toward the grinding wheel axis and along one side surface of the V shape peripheral portion to effect dressing of said surface, and for withdrawing the tool and support after the dressing operation, means effective to advance the other tool and its support inwardly toward the grinding wheel axis and along the other side surface of the V shape peripheral portion to effect dressing of such other surface and for withdrawing the tool and support after such dressing operation, and means automatically operable to separate each tool from the surface dressed when the tool reaches the end of its dressing operation whereby each tool is withdrawn in separated relation to the dressed surface, the parts being so constructed and arranged for operation that as one tool is dressing one of the side surfaces, the other tool is being withdrawn in separated relation to the other side surface.

2. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape with the apex of said portion of substantial width as compared to a sharp edge, which comprises a pair of dressing tools. a support for each tool, means effective to advance one tool and its support axially of the a wheel and then inwardly towards the wheel axis to effect dressing of a portion of the apex and then one side surface of the V shape peripheral portion and for withdrawing the tool and support after the dressing operation. means effective to advance the other tool and its support axially of the wheel and then inwardly towards the wheel axis to dress the remaining portion of the apex and the other side surface of the V shape peripheral portion and for withdrawing the tool and support after such dressing operation, and means automatically operable to separate each tool from the surface dressed when the tool reaches the end of its dressing operation, whereby each tool is withdrawn in separated relation to the dressed surface, the parts being so constructed and arranged for operation that as one tool is dressing one of the side surfaces, the other tool is being withdrawn in separated relation to the other side surface- 3. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape for thread grinding purposes, which comprises a pair of dressing tools, a support for each tool, means effective to move one tool and its support inwardly towards the grinding wheel axis and along one side surface of the V shape peripheral portion to effect dressing of said surface and for withdrawing the tool and support after the dressing operation, and means effective to move the other tool and its support inwardly towards the wheel axis and along the other side surface of the V shape peripheral portion to effect dressing of such other side surface, each of said means including means for moving the tool in a straight line movement towards and from the inner part of the wheel. means moving the tool in a straight line movement back and forth along the wheel axis and means automatically operable to effect separation of the tool from the dressed surface during its return movement following the dressing movement.

4. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape with the apex of said portion of substantial width compared to a sharp edge, which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then'inwardly towards the wheel axis to effect dressing of a portion of the apex and then one side surface of the V shape peripheral portion, means effective to advance the other tool and its support axially of the wheel and then inwardly towards the wheel axis to dress the remaining portion of the apex and the other side surface of the V shape peripheral portion, and adjustable means for varying the two paths of movement of the two tools and tool supports so that grinding wheels having apex portions of varying widths and variably separated side surfaces may be dressed.

5. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape for thread grinding purposes. which comprises a pair of dressing tools, a support for each tool, means effective to move one tool and its support inwardly towards the grinding wheel axis and along one side surface of the V shape peripheral portion to effect dressing of said side surface, means effective to move the other tool and its support inwardly towards the wheel axis and along the other side surface of the V shape peripheral portion to effect dressing of such other side surface, each of said means including means for moving the tool and tool support in a straight line movement towards the inner part of the wheel and means for advancing the tool and support in a straight line movement along the wheel axis, and adjustable means for varying the two paths of movement of the two tools and tool supports so that grinding wheels having variably spaced or separated side surfaces may be dressed.

6. A dressing machine for dressing a grinding wheel, comprising a dressing tool holder, a dressing tool carried by the holder, means for continuedly moving the holder and tool inwardly with respect to the wheel axis and along a side surface of the wheel while maintaining the tool continuously in contact with the surface so that the latter is dressed by the tool in a continued inward stroke and then reversing the movement of the holder and tool so as to effect outward movement of the holder and tool. and means for automatically maintaining the paths of inward and outward movement of the holder and tool substantially separated so that after the tool and holder have completed their continued inward dressing movement, the tool is returned out of contact with the dressed surface. said first means including interengaging relatively rotatable lead screw elements for effecting movement of the holder and tool axially of the wheel and actuated cam means for effecting movement of the holder and tool radially of the wheel.

'7. A dressing machine for dressing a grinding wheel, comprising a dressing tool holder, a dressing tool carried by the holder. means for continuedly moving the holder and tool inwardly with respect to the wheel axis and along a side surface of the wheel while maintaining the tool continuously in contact with the surface so that the latter is dressed by the tool in a continued inward stroke, and then reversing the movement of the holder and tool so as to effect outward movement of the holder and tool, said means including interengaging relatively rotatable lead screw elements mounted in the frame for effecting movement of the holder and tool axially of the wheel and cam actuated means for effecting movement of the holder and tool radially of the wheel, and means for automatically maintaining the paths of inward and outward movement of the holder and tool substantially separated so that after the tool and holder have completed their dressing movement, the tool is returned out of contact with the dressed surface, said last included means comprising means for modifying the action of the screw means when initial reverse movement of the holder takes place.

8. A dressing machine for dressing a grinding wheel, comprising a dressing tool holder, a dressing tool carried by the holder, means for continuedly moving the holder and tool inwardly with respect to the wheel axis and along a side surface of the wheel while maintaining the tool continuously in contact with the surface so that the latter is dressed by the tool in a continued inward stroke, and then reversing the movement of the holder and tool so as to effect outward movement of the holder and tool, said means including interengaging relatively rotatable lead screw elements mounted in the frame for effecting movement of the holder and tool axially of the wheel and cam actuated means for effecting movement of the holder and tool radially of the wheel, and means for automatically maintaining the paths of inward and outward movement of the holder and tool substantially separated so that after the tool and holder have completed their dressing movement, the tool is returned out of contact with the dressed surface, said last included means comprising means for effecting a substantially idling action of the screw means when initial reverse movement of the holder takes place.

9. A dressing machine for dressing a grinding wheel, comprising a dressing tool holder, a dressing tool carried by the holder, means for continuedly moving the holder and tool inwardly with respect to the wheel axis and along a side surface of the wheel while maintaining the tool continuously in contact with the surface so that the latter is dressed by the tool in a continued inward stroke, and then reversing the movement of the holder and tool so as to effect outward movement of the holder and tool, said means in cluding a non-rotatable and a reversely rotatable screw element mounted in the frame one being movable axially by the other and carrying the holder for effecting movement of the tool axially of the wheel, and cam actuated means for effecting movement of the holder and tool radially of the wheel, and means for automatically maintaining the paths of inward and outward movement of the holder and tool substantially separated so that after the tool and holder have completed their dressing movement, the tool is returned out of contact with the dressed surface, said last included means comprising means for effecting axial shifting of the other of said screw elements a limited amount when rotation of the rotatable screw element is reversed.

10. In combination, a frame, non-rotatable and rotatable lead screw means mounted on the frame and engaging ach other, means permitting limited shifting of one of the screw means along its axis, a tool holder movable along said axis with the other screw means after the one screw means is shifted, means for reversing the rotation of said rotary screw means after movement of the tool holder along said axis, and means for effecting an axial shifting of said one screw means within the limits permitted when the rotary screw means is reversed.

11. In combination, a frame, a pair of relatively rotatable lead screw means mounted on the frame and engaging each other, means permitting limited shifting of one of the screw means along its axis, a tool holder movable along said axis with the other screw means after the one screw means is shifted, means for reversing the direction of relative rotation of the screw means after movement of the tool holder along said axis, and means for effecting an axial shifting of said one screw means within the limits permitted when the direction of relative rotation is reversed.

12. In combination, a frame, a pair of relatively rotatable lead screw means mounted on the frame and engaging each other, means permitting limited shifting of one of the screw means along its axis, a tool holder movable along said axis with the other screw means after the one screw means is shifted, means for reversing the direction of relative rotation of the screw means after movement of the tool holder along said axis, means for effecting an axial shifting of said one screw means within thelimits permitted when the direction of relative rotation is reversed, and means for effecting movement of the tool holder transversely of said axis during relative rotation of the screw means.

13. In combination, a frame, a pair of relatively rotatable lead screw means mounted on the frame and engaging each other, means permitting limited shifting of one of the screw means along its axis, tool holders movable along said axis with the other screw means after the one screw means is shifted, means for reversing the direction of relative rotation of the screw means after movement of the tool holders along said axis, means for effecting an axial shifting of said one screw means within the limits permitted when the direction of relative rotation is reversed, and means for effecting movement of the tool holders transversely of said axis during relative rotation of the screw means.

14. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape with the apex of said portion of substantial width as compared to a sharp edge, which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then inwardly towards the wheel axis to effect dressing of a portion of the apex and then one side surface of the V shape peripheral portion and for withdrawing the tool and support after the dressing operation, means effective to advance the other tool and its support axially of the wheel and then inwardly towards the wheel axis to dress the remaining portion of the apex and the other side surface of the V shape peripheral portion and for withdrawing the tool and support after such dressing operation, and adjustable means for varying the distance the tools travel axially of the wheel axis before they travel inwardly towards such axis.

15. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape with the apex of said portion of substantial width as compared to a sharp edge, which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then inwardly towards the wheel axis to effect dressing of a portion of the apex and then one side surface of the V shape peripheral portion and for withdrawing the tool and support after the dressing operation, means effective to advance the other tool and its support axially of the wheel and then inwardly towards the wheel axis to dress the remaining portion of the apex and the other side surface of the V shape peripheral portion and for withdrawing the tool and support after such dressing operation, and a single adjustable means for varying the distance both tools travel axially of the wheel axis before they travel inwardly towards such axis.

16. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape for thread grinding purposes, which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support inwardly toward the grinding wheel axis and along one side surface of the V shape peripheral portion to effect dressing of said surface, and for withdrawing the fool and support after the dressing operation, means effective to advance the other tool and its support inwardly toward the grindin wheel axis and along the other side surface of the V shape 0 peripheral portion to effect dressing of such other surface and for withdrawing the tool and support after such dressing operation, and a singleadjustable means for varying the relative locations of both paths of movement of the tools axially of the wheel so that rinding wheels havin variably spaced side surfaces may be dressed.

1'7. A dressing machine for dressing a rotary grinding wheel having its outer peripheral portion substantially V shape, which comprises a pair of dressing tools. a support for each tool, means effective to advance one tool and its support inwardly towards the wheel axis and along one side surface of the wheel peripheral portion. means effective to advance the other tool and its support inwardly towards the wheel axis and along the other side surface. and a single adjustable means for adjusting the relative locat ons of both paths of movement of the tools axially of the wheel.

18. A dressing machine for dressing a rotary rinding wheel having its outer peripheral portion substantially V shape with the apex of said portion of substantial width as compared to a sharp edge, which comprises a pair of dressing tools. a support for each tool, means effective to advance one tool and its support axiallv of the wheel and then inwardly towards the wheel axis to effect dressing of a portion of the apex and then one side surface of the V shape peripheral portion and for withdrawing the tool and support after the dressing operation. means effective to advance the other tool and its support axially of the wheel and then inwardly towards the wheel axis to dress the remaining portion of the apex and the other side surface of the V shape peripheral portion and for withdrawing the tool and support after such dressing operation, and adjustable means for varying the distance the tools travel axially of the wheel axis operation that as one tool is dressing one of the side surfaces, the other tool is being withdrawn relative to the other side surface.

19. A dressing machine for a rotary grinding wheel having its outer peripheral portion substantially V shape which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then inwardly towards the wheel axis and along one side surface of the V shape portion to effect dressing of such surface and then to withdraw the tool and support, and means effective to advance the other tool and its support axially of the wheel and then inwardly along the other side surface of the V shape portion to effect dressing of such other surface and then to withdraw such tool and support.

20. A dressing machine for a rotary grinding wheel having its outer peripheral portion substantially V shape which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then inwardly towards the wheel axis and along one side surface of the V shape portion to effect dressing of such surface and then to withdraw the tool and support, means effective to advance the other tool and its support axially of the wheel and then inwardly along the other side surface of the V shape portion to effect dressing of such other surface and then to withdraw such tool and support, and means automatically operable to separate each tool from the surface dressed when the tool reaches the end of its dressing operation, whereby each tool is withdrawn in separated relation to the dressed surface.

21. A dressing machine for a rotary grinding wheel having its outer peripheral portion substantially V shape which comprises a pair of dressing tools, a support for each tool, means effective to advance one tool and its support axially of the wheel and then inwardly towards the wheel axis and along one side surface of the v shape portion and then to withdraw the tool and support, so as to effect a dressing operation on the apex portion and on the one side surface before withdrawal of the tool, means effective to advance the other tool and its support axially of the wheel and over the apex portion of the wheel and then inwardly towards the wheel axis and along the other side surface of the V shape portion and then to withdraw the tool and support, so as to effect a dressing operation on the apex portion and the other side surface before withdrawal of the tool, and adjustable means for relatively varying the paths of movement of the two tools and supports so that grinding wheels having apex portions of varying widths and variably spaced side surfaces may be dressed.

IRA J. SNADER.

law-m 

